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HelicopterScale Model RC Helicopters › Tail rotor stops!
08-31-2009 04:13 PM  8 years agoPost 1
AdeH

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Kent, UK

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Well guys as the title suggests....
Here is the problem, but before I strip all the mechanics out. I thought I would pose this one to the forums.

Here goes. (I am just in the throws of fight testing the new project)
I have Vario benzin mechanics driving a Len Mount flexi drive to the tail.
As I spool up everything looks and sounds perfect.
Just as the heli is about to go light on the skids, the tail stops. Literally just stops.
So wind down and shut down.
Upon investigation the take off gearing appears fine they turn with no problems, the connector to the flexi drive is fine. In fact everything turns beautifully by hand. It's as soon as you put spool up again.

Anyone any ideas without having to strip mechanics out again. I sounds like something is slipping but no idea what.

Any thoughts/advice/feedback gratefully received.

Cheers
Ade

After scale everything else is a toy!

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08-31-2009 04:16 PM  8 years agoPost 2
Copter Doctor

rrProfessor

Enterprise/ft.rucker ,al- home of army aviation

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sounds like you have a gear mesh problem. also id the cable isnt supported along the tailboom, it can move causing gears in the front of the mechs to lose mesh and contact as well.

drive a rotary, fly a rotorcraft

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08-31-2009 04:28 PM  8 years agoPost 3
AdeH

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Kent, UK

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Cheers copterDr.

Oh yeah, thanks for the reminder..

Sorry forgot to add cable is running in teflon and brass tubes as per normal, and tube is secured along its length again as per norm.

Ade

After scale everything else is a toy!

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08-31-2009 04:45 PM  8 years agoPost 4
Dr.Tim

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Mojave Desert

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Make sure the couplers are Properly Tightened, If they are then it's not the flex Drive and something else ... Really sounds though as if the couplers are NOT TIGHT.

Dr.Tim

From Simple minds come simple ideas! Approach Engineering

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08-31-2009 04:48 PM  8 years agoPost 5
wingtip

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Indiana

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my thoughts exactly tim...

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08-31-2009 04:58 PM  8 years agoPost 6
AdeH

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Kent, UK

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nope

Hiya Guys
Thanks for the advice. The couplers are as tight as a tight thing.
That was one of the things I already checked. Everything I can see that should be screwed/locktite'd is.

As I say when turned manually, everythign spins lovely.
As soon as you add engine and spool up it goes wrong.

Cheers
Ade

After scale everything else is a toy!

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08-31-2009 05:02 PM  8 years agoPost 7
Joel Rosenzweig

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Marlborough, MA - USA

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Maybe the frames, or something in the TR drive setup are twisting under load, causing the TR drive to disengage. Possibly it's just a bit too short?

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08-31-2009 06:17 PM  8 years agoPost 8
Dr.Tim

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Mojave Desert

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Also Check the setscrews on the gear in the tailrotor gearbox, I had one come loose ONCE! As I recall it did something simular .. it would SLOW under load .. took me awhile to figure out what was going on.

Dr.Tim

From Simple minds come simple ideas! Approach Engineering

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08-31-2009 06:49 PM  8 years agoPost 9
AdeH

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Kent, UK

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Thank you

Thanks I tried them too they were all tight and as they should be.

After scale everything else is a toy!

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08-31-2009 06:59 PM  8 years agoPost 10
Copter Doctor

rrProfessor

Enterprise/ft.rucker ,al- home of army aviation

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hmmmm, this is puzzling.
if there was an issue with a loose set screw, while you would lose drive, it would still spin though it would be noticeably slower. if it is in fact coming to a stop, that means somewhere along the drivetrain, gears are moving completely apart from each other and the two that comes to mind would be the ones in the mechs themselves. maybe the gears are tight on the shaft but the shaft, one of them, is shifting. could also be the same in the t/r gearbox. this is very puzzling
please let us know what you find to be the culprit.

drive a rotary, fly a rotorcraft

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08-31-2009 07:36 PM  8 years agoPost 11
wingtip

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Indiana

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If its losing tail as you spool up under load/torque, then hold the tail pinion gear (rides on top the crown gear) and spin the tail rotor by hand pretty hard to see where the slippage is...

it has to be something at the:
1)crown gear pinion gear,
2)front coupler..
3)or even the drive wire coming undone if its not double wound and installed in the wrong direction...
4) at the tail box coupler
5) tail gears...

heck it could even be as your spooling up with a bunch of negative in it , its pushing the mainshaft down (frames flexing/giving) shoving the crown gear down and away from the pinion gear... try lifting/pushing on the mainshaft and see if you can move the shaft/frames..

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09-01-2009 08:02 PM  8 years agoPost 12
AdeH

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Kent, UK

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Solved it!

Well thanks to everyone who offered advice.
It was a grubscrew!

In the TR gears there is one that runs to a shaft and out through a set of bearings, then on to the tail. (the horizontal one)
The shaft was only 1/2 way through, so when looking down into the hole (after taking the set screw/grubscrew out), you could see half a shaft and half nothing.

It looks like the flexidrive connector had slightly more shaft then it needed (greedy thing!)
So moved the shaft up and more into the gears and hey presto, all screwed down it works!

Again thanks everyone.

Happy landings.

Adrian

After scale everything else is a toy!

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09-02-2009 12:26 AM  8 years agoPost 13
Copter Doctor

rrProfessor

Enterprise/ft.rucker ,al- home of army aviation

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sweeet!!! see now, that was going to be my next guess, that darn grub screw!!
glad that mystery is solved and now time to continue.

drive a rotary, fly a rotorcraft

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09-02-2009 12:44 AM  8 years agoPost 14
Dr.Tim

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Mojave Desert

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I think I already said that in an earlier post!

From Simple minds come simple ideas! Approach Engineering

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09-02-2009 08:57 AM  8 years agoPost 15
AdeH

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Kent, UK

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I know!

Yes yes Dr Tim is the all seeing guru.

In my defence, the screw was as tight as can be, but it was only tight on half of the shaft!

Again thanks to all for the advice, feedback and inspiration!

Regards
Ade

After scale everything else is a toy!

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09-02-2009 03:07 PM  8 years agoPost 16
Dr.Tim

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Mojave Desert

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More of the "Babbling Idiot!" .. Glad you found the issue and the problem has been resolved!!

Dr.Tim

From Simple minds come simple ideas! Approach Engineering

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